FIG. 1 is a structural block diagram of a receiver in an existing radio communications system. As shown in FIG. 1, the receiver mainly includes an analogue radio-frequency front end 101, an analogue demodulator and intermediate-frequency channel 102, and an analogue-to-digital converter (Analogue to Digital Converter, ADC) 103. The analogue radio-frequency front end 101 generally includes a low noise amplifier (Low Noise Amplifier, LNA). Generally, various receivers in the radio communications system all have the non-ideal characteristics. For example, for an analogue IQ demodulation receiver, the non-ideal characteristics thereof are reflected in unbalanced amplitudes and phases of in-phase and quadrature (Inphase and Quadrature, IQ) signals, direct current (Direct Current, DC) interference, an in-band amplitude ripple and a group delay ripple in a radio-frequency filter of an analogue radio-frequency front end, non-linear distortion, and so on. For a digital intermediate-frequency receiver, the non-ideal characteristics thereof are reflected in an in-band amplitude ripple and a group delay ripple in a radio-frequency filter, an in-band amplitude ripple and a group delay ripple imported by an intermediate-frequency surface acoustic wave (SAW) filter, non-linear distortion, and so on.
In practical use, a correction channel is often used to correct the non-ideal characteristics of a receiver. Currently, a commonly used method for correcting a channel is that a test signal producing device is used to produce a radio-frequency test signal in a certain form, and at an input end of a receiver, the radio-frequency test signal and an input radio-frequency analogue signal are mixed by using a coupler or a resistor network and are sent to the input end of the receiver together. The test signal producing device further sends a signal of a digital form corresponding to the radio-frequency test signal to a channel correction module to be corrected by the channel correction module. After the correction performed by the channel correction module, cancellation processing is performed on the test signal, so as to attempt to eliminate the interference of the test signal to a service signal.
However, the cancellation processing performed on the test signal is not completely ideal, and a signal output after the cancellation processing still has certain residues of the test signal, which causes the interference to the service signal.